Bafang error 04: Throttle not in home position
At power-up the controller measured a throttle voltage above idle, so it refuses to start assist as a safety measure. The rider sees the code immediately after switching on and gets no motor power. It clears once the throttle reads its rest voltage again.
Likely causes
- Throttle was pressed or bumped while switching the bike on
- Sticky or worn thumb/twist throttle that does not fully spring back
- Water or corrosion in the throttle connector raising the signal voltage
- Damaged throttle hall sensor or broken signal wire
- Wrong throttle plugged in (5V signal range not matching the controller)
How to fix Bafang error 04
- Switch off, let the throttle rest, switch on again without touching it
- Check the throttle returns freely; clean grit around the spring and lever, re-grease if needed
- Unplug the throttle and power on: if the code is gone, the throttle or its cable is faulty
- Open the throttle connector, dry it, clean corrosion with contact cleaner and re-seat
- Replace the throttle (inexpensive, plug-and-play on Bafang connectors)
- If the code remains with the throttle disconnected, the controller throttle input is at fault: shop
Warranty: Bafang parts are usually sold through dealers or online resellers; warranty is typically 1-2 years via the seller, and this code alone is rarely a warranty claim.
Typical cost: A Bafang-compatible throttle costs about EUR/USD 15-40; a controller repair is EUR/USD 80-200.
Frequently asked
How do I reset Bafang error 04?
Power cycle without touching the throttle. If it returns, the throttle is not resting at its idle voltage and needs cleaning or replacement.
Can I keep riding with error 04?
Yes, you can pedal home, but assist stays off until the throttle reads idle. Some bikes allow pedal assist to resume after unplugging the throttle.
Is a throttle fault covered by warranty?
Usually only in the first months; after that a throttle is treated as a wear item.
Related Bafang codes
Not an official Bafang document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.